3.0 T磁共振正常肝、脾及肾R_2~*及T_2~*值的测量

目的 研究正常成人肝、脾、肾磁共振R_2~*和T_2~*值的正常范围.方法 对85例健康成人进行3.0T磁共振多回波R_2~*扫描,利用R_2~* map和T_2~* map分别测量肝、脾、肾实质及髓质、脊柱旁肌肉的T_2~* 和R_2~*值,再分别计算T_2~*、R_2~*值的肝/肌、肝/脾及脾/肌比值.分析性别、年龄对MR测量参数的影响.结果 男性及女性的脾R_2~* 值分别为(59.42±16.61)Hz和(51.17±15.49)Hz,具有统计学差异(P=0.020,t=2.514);男性和女性的肝/脾T_2~*比值分别为0.87±0.35、0.79±0.33,也具有明显差异(P=0.039,t=2.231);而其余测量参数在性别之间未见统计学差异(P>0.05).所有测量值与年龄之间也未见相关性(P>0.05).肝、脾的R_2~*值及T_2~*值均大于肌肉和肾脏(P<0.05),而肾皮质的T_2~*值为(37.88±15.55)ms,明显大于肾髓质的(28.10±9.01)ms(P=0.021,t=2.315);但R_2~*值在皮、髓质之间未见差异(P>0.05).肝、脾之间的R_2~* 和T_2~*值,以及3个比值(肝/肌肉、脾/肌肉及肾/肌肉)之间均未见统计学差异(P>0.05).结论 利用MR多回波R_2~*技术测得的正常成人肝、脾、肾的T_2~*、R_2~*值及其比值可为组织铁沉积及血氧水平的评估提供界定范围.     

侧位双能X线吸收测量学测量胸腰椎骨矿含量的准确性:体模研究

椎体骨折是脊柱骨质疏松的最重要表现之一。临床上应用双能吸收测量学估价椎体骨折危险性,是根据骨矿含量(BMC)的测定,或骨矿密度(BMD),即BMC除扫描面积得出的测量值来进行估价的。作者这项研究的目的在于以体模实验方式确定侧位DXA测量胸腰椎BMC的准确性,并检验胸椎BMC及BMD的节段性变异。方法:对9具经福尔马林浸泡的脊柱进行尸体解剖得到T_1～L_5段椎骨,普通X线片检查排除了样品存在有骨病、     

磁共振波谱技术在腰椎原发性骨质疏松中的诊断价值

目的探讨磁共振(MR)波谱脂肪测量技术评估腰椎原发性骨质疏松的价值。方法利用1.5T MR波谱(MRS)及双能X线吸收法(DXA)对56例研究对象进行检查,收集腰椎L3椎体脂肪比(FF)及L1~4椎体骨密度(BMD)值,以T值-2.5为临界点分为2组,将T值>-2.5定为阴性组和T值≤-2.5定为阳性组,采用Pearson法对FF-MRS与BMD作相关性分析。结果阴性组与阳性组之间的FF及BMD差异均有统计学意义(P<0.01),FF与BMD平均值存在高度负相关关系(r=-0.806,P<0.01)。结论MR波谱因其在评估骨质量方面有较好的优势,可为原发性骨质疏松评估提供一个有效的辅助方法。     

健康老年妇女近段股骨骨密度和结构的定量CT研究

目的 采用定量CT(QCT)和双能X线吸收测量(DXA)仪对健康老年妇女近段股骨骨密度(BMD)和骨结构进行研究,并对2种测量方法的结果进行比较.方法 对66名65岁以上健康妇女左侧髋关节进行DXA测量,计算出股骨颈和粗隆区BMD;对其双侧近段股骨进行QCT测量,计算出股骨颈、粗隆区和整体股骨ROI的皮质骨、松质骨和总体骨的BMD和体积;并将QCT三维图像模拟DXA的平面投影计算出模拟DXA股骨颈BMD和模拟DXA股骨粗隆区BMD.对所获数据进行配对t检验或非参数秩和检验,并用Pearson法分析DXA和QCT相对应ROI的相关性.结果 用QCT可以对股骨近段不同ROI(股骨颈、粗隆区和整体股骨区)及不同骨成分(皮质骨、松质骨和总体骨)的BMD及体积等参数进行精确的定量分析.除右侧股骨颈皮质骨BMD[(0.52±0.04)g/cm3]、股骨粗隆区皮质骨BMD[(0.49±0.03)g/cm3]、股骨粗隆区综合骨BMD[(0.22±0.04)g/cm3]大于左侧相应参数[分别为[(0.51±0.04)、(0.48±0.03)、(0.21±0.04)g/cm3],差异均有统计学意义(P值均<0.05),但差别均<3.3%;而模拟DXA股骨颈BMD、模拟DXA股骨粗隆区BMD、股骨颈皮质骨体积、股骨颈松质骨BMD、股骨颈松质骨体积、股骨颈综合骨BMD、股骨颈综合骨体积、股骨粗隆区皮质骨体积、股骨粗隆区松质骨BMD、股骨粗隆区松质骨体积、股骨粗隆区综合骨体积左侧参数分别为(0.52±0.10)g/cm2、(0.78±0.13)g/cm2、5.80 cm3、(0.06±0.03)g/cm3、(5.19±1.40)cm3、(0.25±0.04)g/cm3、15.66 cm3、(21.74±3.43)cm3、(0.08±0.03)g/cm3、(34.27±6.09)cm3、(76.12±11.11)cm3,右侧分别为(0.52±0.10)g/cm2、(0.78±0.13)g/cm2、6.01 cm3、(0.06±0.02)g/cm3、(5.17±1.27)cm3、(0.25±0.04)g/cm3、15.62 cm3、(22.12±3.60)cm3、(0.09±0.03)g/cm3、(34.17±5.94)cm3、(76.53±10.71)cm3,差异均无统计学意义(P值均>0.05).左右两侧近段股骨QCT各相对应参数之间的r值范围在0.656～0.955,均具有相关性(P<0.05).QCT模拟DXA股骨颈和粗隆区BMD与真正DXA测量的相应值之间r值分别为0.685和0.855,具有相关性(P<0.05).结论 利用QCT技术可以对老年妇女近段股骨不同区域和不同成分的BMD和结构进行精确定量分析,QCT是骨质疏松研究中非常有用的测量技术.     

VQCT与DXA测量骨密度的相关性研究

目的　探讨VQCT与DXA测量骨密度诊断骨质疏松症的相关性。方法　 5 2名患者 ,男 2 4例 ,女 2 8例 ,平均年龄 5 1岁 ,先后进行DXA和VQCT检查 ,对所获得的数据进行相关性分析。结果　按照WHO的骨密度测量诊断骨质疏松症标准 ,髋部DXA检查 (F -DXA)中有 14人 ,腰椎DXA检查 (S -DXA)中有 9人 ,腰椎VQCT检查 (S -VQCT)中有 2 3人被诊断为骨质疏松 ,分别占患者总人数的 2 8% ,18%和 46%。用SPSS统计软件对它们的T评分分别做配对的t检验 ,结果显示S -VQCT的检查结果与F -DXA和S -DXA均有显著性差异 (Ρ <0 .0 5 ) ,S -VQCT与F -DXA有显著相关性 ,相关系数为 0 .864 (Ρ <0 .0 5 ) ,而与S -DXA相关性无统计学意义。结论　VQCT所测量的腰椎BMD与DXA所测量的髋部BMD有显著相关性 ,而与DXA所测量的腰椎BMD无显著相关性     

梯度回波采样自旋回波序列测量脑R2'及氧摄取分数值稳定性及重复性的研究

目的 通过梯度回波采样自旋回波序列(GESSE)测量脑组织R2'值与传统梯度回波序列(GRE)间接测量R2'值的方法在正常志愿者内进行比较,初步评价该序列的稳定性及重复性.方法 8名正常健康志愿者,平静状态下进行头颅单层GESSE序列和该层面T2图(T2 map)和有效横向弛豫时间图(T2*map)扫描.1 d之后,再重复进行相同层面的上述序列扫描.应用北大医院和北京大学工学院生物医学工程系共同自主开发的软件对GESSE序列原始图像进行后处理得到R2'图(R2'map)及氧摄取分数图(OEF map),将左、右大脑半球等分为前、中、后3个区域,测量该区域R2'值和OEF值;T2 map及T2*map的数据在Functool工作站上进行后处理得到自旋-自旋弛豫率图(R2 map)和表观自旋-自旋弛豫率图(R2*map),利用公式计算得到R2'值(R2'=R2*-R2,R2*=1/T2*,R2=1/T2),ROI测量方法及部位同GESSE序列.通过配对t检验比较GESSE序列及传统序列2次测得R2',初步评价该序列的稳定性,通过配对t检验比较GESSE序列前后2次扫描得到的OEF值,初步判断该序列测量OEF值的重复性.结果 GESSE序列前后2次扫描得到的R2'值分别为(4.21±0.92)、(4.45±0.94)Hz,差异无统计学意义(t=-0.83,P＞0.05).前后2次传统方法得到R2'平均值分别为(7.37±1.47)、(6.42±2.33)Hz,差异有统计学意义(t=1.80,P＜0.05),第1次GESSE序列和传统方法所测R2'差异有统计学意义(t=1.71,P＜0.05).GESSE序列前后2次所测OEF值分别为0.327±0.036和0.336±0.035,差异无统计学意义(t=-1.48,P＞0.05).结论 在正常被试者中GESSE序列测量R2'值与传统方法相比稳定性较好.GESSE序列测量的OEF值重复性较好.该技术有进一步临床应用的前景.     

T_2WI与T_2 * mapping技术在腰椎间盘MR成像中的应用

目的探讨T_2WI(T_2-Weighted images)及T_2*mapping技术在腰椎间盘磁共振成像(magnetic resonance imaging,MRI)中的应用。方法收集来我院行腰椎间盘MR扫描患者71例(均无手术史及内固定、无MR扫描禁忌),71例患者行常规MR扫描,在斜矢状位(oblique saggital,OSag)L1/L2~L5/S1各个椎间盘髓核内放置感兴趣区(region of interest,ROI),并测量T_2WI信号强度(signal intensity,SI)值。其中,36例患者同时行T_2*mapping MRI扫描,并于OSag L1/2~L5/S1测量ROI内T_2WI SI值及T_2*值。分析并比较腰椎间盘髓核T_2WI SI值与T_2*值的差异。结果各组L4/L5和L5/S1SI值相近且均明显低于L1/L2,L2/L3,L3/L4椎间盘的T_2WI SI值;按Pfirrmann’s分级法将各椎间盘按Ⅰ~Ⅴ分级,T_2WI SI值与T_2*值均随着Ⅰ~Ⅴ组而信号逐渐降低,且T_2*值较同组T_2WI SI值大幅降低。其中,按Pfirrmann’s分级法第Ⅰ组中两者的个数存在统计学差异(P0.05),其余四组未见明显统计学差异(P0.05)。结论T_2WI与T_2*mapping MR技术都可以反映腰椎间盘退变的影像学依据;而T_2*mapping成像技术在髓核T_2*弛豫时间值的空间变化可量化反映椎间盘退变早期髓核的生化状态,为诊断腰椎间盘早期退变提供影像学依据。     

颅内颈动脉闭塞之MRI

作者分析了7例颅内颈动脉闭塞之 MRI。女性4例,男性3例。年龄33～65岁。分别使用1.5T(4例)和1.5,0.5T(3例)超导磁体。均采用多层面自旋回波(SE)脉冲序列;前4例以质子密度 T_1及 T_2加权成象(用双回波);后3例以T_1和单回波 T_2加权成象。成象参数分别是 T_1加权象:500～1000/25～30/2;质子密度象:2000/20～35;T_2加权象:60～120/2。层厚5mm,间隔0～2mm,矩阵128~2和256~2。病人多做了横断、冠状和/或矢状面扫描。MR 扫描在发病后4～60天(平均21.4天)进行。     

平片能发现骨质减少吗?

作者对比研究了骨质减少的胸腰椎平片主观评估,和用双能X线吸收仪(DXA)扫描腰椎、股骨颈部测量的骨矿物密度(BMD),还有椎体变形与BMD的关系。随机选择的200例中,男性107例年龄52～90岁(平均65.7岁),女性93例年龄52～82岁(平均63.9岁)。脊椎T_4～L_5标准侧位片以T_7、L_2为中心分两次投照。前后位腰椎和左髋股骨颈部测量使用XR26DXA(BMD为g/cm~2),活体精度校准     

应用MR多回波⊿R2~*磁敏感校正技术确定肿瘤血容量

<正>目的探讨多回波磁敏感校正MR弛豫技术⊿R2*值的准确测量,能否作为无创性评价肿瘤灌注血容量的替代参数。材料与方法所有实验均经动物保护机构委员会批准。体模为玻璃管内不同浓度超顺磁     

Assessment of the skeletal status by MR relaxometry techniques of the lumbar spine: comparison with dual X-ray absorptiometry

Purpose: To measure lumbar spine T2*, T2, T2′ and T1 MR relaxometry parameters and compare them with lumbar spine bone mineral density (BMD) in a group of postmenopausal women. Materials and methods: Lumbar spine T2*, T2, T2′ and T1 MR relaxometry parameters and BMD values were assessed in 101 postmenopausal women (mean age: 61.8±7.1 (1 S.D.) years); of them 63 referred to as control subjects (group A, BMD T-scores ≥ −2.5 S.D.) and 38 as osteoporotic (group B, BMD T-scores < −2.5 S.D.). All magnetic resonance imaging (MRI) examinations were performed on an 1.5 T imaging system using: (a) a 2D single slice multi echo (32 echoes) gradient echo (MEGRE) sequence (TR/TE1/TE32/FA: 160/2.7/74.93 ms/25°) for the T2* measurement, (b) a respiratory gated 2D single slice Multi Echo (16 echoes) Spin Echo (MESE) sequence (TR/TE1/TE16/FA: 2000–2500/22.5/360 ms/90°) for the T2 measurement and (c) a 2D single slice multi TI (18 repeats) turbo Fast Low Angle Shot (turbo FLASH) sequence (TR/TE/TI1/TI16/FA: 11/4.2/10/5000 ms/10°) for the T1 measurement. T2′ was calculated from its definition equation: (1/T2′ = 1/T2* − 1/T2). Lumbar spine BMD was assessed using DXA. Results: All measured parameters showed statistically significant differences between groups A and B (from P<0.05 to <0.001). All parameters showed significant associations with subject’s age ranging from r=0.245 (P<0.05) for the T2 up to r=0.377 (P<0.001) for the T2*. All parameters showed significant associations with subject’s BMD measurements ranging from r=−0.184 (P<0.05) for the R1 = (1/T1) up to r=−0.345 (P<0.0005) for the T2. Conclusion: Among the MR relaxometry parameters studied, T2* and T2 showed better discrimination of patients with osteoporosis from control subjects.     

猴可复性大脑中动脉闭塞模型脑缺血半暗带的血氧水平依赖效应

目的 探讨血氧水平依赖(BOLD)MRI对确定猴脑缺血半暗带(IP)的价值.方法 成年恒河猴6只,应用微导管法制作猴可复性大脑中动脉闭塞(MCAO)模型.MCAO后0 h、再灌注后1、3、 6、 12、24及48 h分别进行DWI、PWI、T_2 WI、定量T_2和T_2~* 扫描,根据T_2和T_2~* 图计算可逆性横向弛豫率(R_2'),用来表示BOLD效应(R_2' BOLD).计算动脉闭塞期DWI(0 h DWI)、再灌注48 hT_2WI(48 h T_2WI)及脑组织大体切片2,3,5-氯化三苯基四氮唑(TTC)染色病灶体积百分比(病灶体积/双侧大脑半球体积).将缺血组织划分为3个区域:梗死核心(0 h DWI、48 h T_2WI均为高信号区)、IP(0 h DWI高信号,48 h T_2WI等信号区)及低灌注区(0 h平均通过时间延长但0 h DWI、48 hT_2WI均为等信号区),分别测最3个区域R_2'的相对值(患侧/健侧半球镜影区比值,rR_2').病灶体积比比较采用配对t检验和相关分析,3个区域rR_2'比较采用单因素方差分析.结果 6只猴中4只造模成功.48 h _T2WI病灶体积比(8.16±0.55)%较0 h DWI的(11.37±1.41)%明显缩小(t=6.472,P<0.05);TTC染色病灶体积比(8.15±0.62)%与48 h T_2WI的(8.16±0.55)%差异无统计学意义(t=0.150,P>0.05),两者呈明显正相关(r=0.98,P<0.05).梗死核心、IP、低灌注区rR_2'在各时间点差异均有统计学意义,梗死核心低于IP,IP低于低灌注区(P<0.05),三者rR_2'值:0 h时分别为1.129±0.108、1.329±0.081、1.584±0.103(F=36.19,P<0.05).1 h分别为0.668±0.082、1.237±0.072、1.435±0.066(F=134.09,P<0.05).3 h分别为0.536±0.075、1.453±0.081、1.770±0.141(F=256.30,P<0.05).6 h分别为0.259±0.050、2.435±0.131、2.957±0.177(F=803.25,P<0.05).12 h分别为0.385±0.054、2.447±0.148、3.254±0.184(F=743.74,P<0.05).24 h分别为0.083±0.026、1.968±0.127、3.101±0.144(F=1236.26,P<0.05).48 h分别为0.246±0.058、3.694±0.218、4.297±0.322(F=557.02,P<0.05).随再灌注时间延长,IP和低灌注区的rR_2'呈逐渐升高趋势,表现为负性BOLD效应;梗死核心呈逐渐降低趋势,表现为正性BOLD效应.结论 R_2' BOLD可以根据缺血脑组织氧代谢状态的不同来区分IP和梗死核心.     

MR relaxometry of lumbar spine, hip, and calcaneus in healthy premenopausal women: relationship with dual energy X-ray absorptiometry and quantitative ultrasound

This study evaluates if the reversible transverse relaxation rate (R2') assessed in vivo by MR of lumbar vertebrae, hip, and calcaneus is correlated with dual energy X-ray absorptiometry (DXA) and to quantitative ultrasound (QUS) of the calcaneus. Fifteen healthy premenopausal women aged 23-47 years were studied by DXA, QUS, and MR relaxometry. The GESFIDE sequence was used to separate the FID rate (R2*) into its two components, the non-reversible transverse relaxation rate (R2) and the reversible transverse relaxation rate (R2'). Long-term reproducibility was obtained by repeated measurements of hip and calcaneus in nine individuals after 300+/-89 days. R2' and R2* of the calcaneus had a relationship to broad-band ultrasound attenuation (BUA; r = 0.46, both p<0.05), but not to other US or DXA parameters of the calcaneus. Both R2' and R2* were correlated with bone mineral per area (BMA) of the hip (r>0.73, p<0.001 and r>0.66, p<0.01, respectively). R2 was correlated with BMA(L1-L4) (r = 0.52, p<0.05). R2' and R2* were not correlated with BMA(L1-L4). When the right and left sides were compared in calcaneus and hip the correlation coefficient for R2' and R2* ranged from 0.76 to 0.86 (p<0.001). The long-term reproducibility expressed in coefficient of variation (CV%) was approximately 5 % for R2' and approximately 4% for R2*. Differences in R2 between individuals were not reproducible. The results of this study indicate that R2' and R2* measurements are reproducible and might be of value when evaluating bone quality of the hip and foot.     

绝经后妇女腰椎骨密度容积性定量CT测量研究

目的 应用容积性定量CT(vQCT)技术和双能X线吸收测量(DXA)仪测量绝经后妇女腰椎容积性骨密度(BMD),评价2种检查方法区分骨质疏松伴椎体骨折与骨质疏松不伴骨折的差异.方法 选取绝经后妇女118名[平均年龄(62.1±7.0)岁],按照所行胸腰椎X线平片检查结果及腰椎DXA测量的参数[前后位BMD(AP-SPINE)]值分组,>均值-1个标准差(x-1s)为正常组、x-1s～x-2s为骨量减少组、0.05).在骨质疏松组和骨质疏松伴骨折组AP-SPINE仅与3D-CORT间有相关性(R2=0.189,P<0.01);App60 BV/TV%、App80 BV/TV%、App100 BV/TV%、App120 BV/TV%与3D-TRAB或2D-TRAB之有相关性(3D法:R2值分别为0.955、0.951、0.941、0.912;2D法:R2值分别为0.912、0.910、0.878、0.821;P值均<0.01).容积性BMD的测量精确度为0.70%～2.25%.结论 vQCT技术可区分骨质疏松及伴骨质疏松性骨折绝经后妇女骨量,能力高于DXA,其中整体骨BMD诊断严重骨质疏松的效果最好;App BV/TV%可反映骨质疏松者骨小梁丢失程度,预测骨折风险.     

~1H-MRS与DWI在骨质疏松症中的初步应用

目的 探讨绝经后女性腰椎骨髓脂肪分数(fat fraction,FF)、表观扩散系数(apparent diffusion coefficient,ADC)值与骨密度(bone mineral densities,BMD)的关系.资料与方法 将行腰椎双能量X线吸收测定(dual X-rayabsorptionmetry,DXA)的60例绝经后女性根据T值分为3组:骨质正常组(T>-1.0)20例,骨质减少组(T=-1.0～-2.5)20例,骨质疏松组(T<-2.5)20例.所有研究对象均行氢质子磁共振波谱分析(~1H MR spectroscopy,~1H-MRS)、MR扩散加权成像(diffusion weighted imaging,DWI),分别测定L_3椎体FF和ADC值.采用组间t检验对不同骨质组间FF、ADC值差异进行统计学分析.采用Pearson相关分析3组间FF、ADC值与BMD的相关性. 结果骨质疏松组脂肪含量[(59.1±8.8)%,P=0.003]与骨质减少组脂肪含量[(54±7.6)%,P=0.039]均比骨质正常组[(49±9.1)%]高.骨质疏松组比骨质减少组椎体脂肪含量高(P=0.045).椎体骨髓ADC值与T值无相关性.所有绝经后女性患者FF值与T值呈负相关(r=-0.46,P<0.01),与ADC值间呈轻度负相关(r=-0.25,P<0.05),但骨质疏松组中FF值与ADC值间呈较明显负相关(r=-0.72,P<0.01).ADC值与T值无相关性(r=0.315,P>0.05).结论 绝经女性椎体骨髓脂肪含量随着BMD的减小而增大.MRS可作为BMD检查的辅助手段.MRS与DWI可以无创性了解骨质疏松症患者骨髓的生理、病理变化,单纯DWI并不能反映BMD的改变.     

Comparison of bone mineral density and quantitative ultrasound of the calcaneus: site-matched correlation and discrimination of axial BMD status

The performance of quantitative ultrasound (QUS) and dual energy X-ray absorptiometry (DXA) bone densitometry of the calcaneus have been compared, both in terms of site-matched correlation and their discriminatory ability to identify osteoporotic and osteoporotic or osteopenic subjects. 91 female subjects (aged 56.9 +/- 9.6 years, 31-84 years) who were routinely referred for axial BMD assessment of the lumbar spine and femoral neck by DXA (Lunar DPX-L), consented to have additional measurements of QUS (McCue CubaClinical Mk II) and DXA (Lunar PIXI) of their left calcaneus. The site-matched correlation between calcaneal BMD with QUS parameters were: (a) broadband ultrasound attenuation (BUA) alone, adj-R2 = 62.7%, p < 0.0001; (b) velocity (VOS) alone, adj-R2 = 48.4%, p < 0.0001; and (c) BUA and VOS combined, adj-R2 = 65.2%, p < 0.0001. The site-matched correlations are towards the higher end of data reported by other researchers, indicative of the exacting measurement protocol implemented here. 30 subjects were categorized as normal, 38 being osteopenic and 23 being osteoporotic. Optimum accuracies and odds ratios were obtained using logistic regression. The differences in accuracy between calcaneal BMD and calcaneal QUS parameters were statistically insignificant, with zero included within the confidence intervals, for the identification of both (a) osteoporotic and (b) osteoporotic or osteopenic subjects. The odds ratios for the discrimination of subject status achieved with calcaneal BMD were higher, although statistically insignificant, than achieved with the QUS parameters. Receiver operator characteristic (ROC) analysis for the identification of subjects into the categories (a) and (b) above was performed. Areas under the ROC curve (AUC) (95% confidence intervals) for the logit of the probability that a subject would be osteoporotic were: 0.814 (0.700, 0.928) for calcaneal BMD; 0.791 (0.673, 0.909) for BUA; 0.717 (0.588, 0.846) for VOS; and 0.793 (0.675, 0.911) for BUA and VOS combined. For the identification of osteoporotic or osteopenic subjects, the ROC areas were: 0.851 (0.774, 0.928) for calcaneal BMD; 0.773 (0.678, 0.868) for BUA; 0.783 (0.690, 0.877) for VOS; and 0.778 (0.685, 0.871) for BUA and VOS combined. Again, calcaneal BMD provided a higher, yet statistically insignificant, AUC than any QUS parameter. In conclusion, for the identification of subjects defined by World Health Organization criteria for axial BMD, the performance of BMD and QUS calcaneal parameters were statistically comparable. The choice of peripheral bone densitometry modality should therefore be made upon factors external to their discriminatory performance.     

Lean body mass and leg power best predict bone mineral density in adolescent girls

PURPOSE: We evaluated anthropometric and performance measures that best predict bone mineral density (BMD) and bone mineral content (BMC) in 54 adolescent girls (14.6 +/- 0.5 yr; 22.7 +/- 14.0 months past menarche). METHODS: Whole body, femoral neck, greater trochanter, lumbar spine (L2-L4), and mid-femoral shaft BMD and BMC, and whole body bone-free lean mass and fat mass were assessed using DXA (Hologic QDR 1000/W). Knee extensor strength and leg power were assessed by isokinetic dynamometry and the Wingate Anaerobic Power Test, respectively. RESULTS: Whole body lean mass was correlated with BMD at all bone sites (r = 0.45-0.77; P < 0.001) and was more highly correlated with bone at all sites than was body weight. Leg power was also associated with BMD at all sites (r = 0.41-0.67; P < 0.001), whereas leg strength correlated significantly with all sites (r = 0.41-0.53; P < 0.001) except the lumbar spine. Stepwise regression analyses revealed that 59% of the variance in whole body BMD was predicted by lean mass alone. No other variables, including fat mass, height, months past menarche, leg power, or leg strength, contributed additionally to the regression model. Similarly, lean mass was the only predictor of lumbar spine and femoral shaft BMD (R2 = 0.25, R2 = 0.37, respectively), while femoral neck and trochanteric BMD were best predicted by leg power (R2 = 0.38, R2 = 0.36, respectively). Similar but stronger models emerged using BMC as the outcome, with lean mass and leg power explaining the most variance in BMC values. CONCLUSION: In this group of adolescent girls, lean body mass and leg power best predicted BMC and BMD of the whole body, lumbar spine, femoral shaft, and hip, which may suggest an important role for muscle mass development during growth to maximize peak bone density.     

Advances in osteoporosis imaging

In the assessment of osteoporosis, the measurement of bone mineral density (BMD_a) obtained from dual energy X-ray absorptiometry (DXA; g/cm²) is the most widely used parameter. However, bone strength and fracture risk are also influenced by parameters of bone quality such as micro-architecture and tissue properties. This article reviews the radiological techniques currently available for imaging and quantifying bone structure, as well as advanced techniques to image bone quality.With the recent developments in magnetic resonance (MR) techniques, including the availability of clinical 3 T scanners, and advances in computed tomography (CT) technology (e.g. clinical Micro-CT), in-vivo imaging of the trabecular bone architecture is becoming more feasible. Several in-vitro studies have demonstrated that bone architecture, measured by MR or CT, was a BMD-independent determinant of bone strength. In-vivo studies showed that patients with, and without, osteoporotic fractures could better be separated with parameters of bone architecture than with BMD. Parameters of trabecular architecture were more sensitive to treatment effects than BMD. Besides the 3D tomographic techniques, projection radiography has been used in the peripheral skeleton as an additional tool to better predict fracture risk than BMD alone.The quantification of the trabecular architecture included parameters of scale, shape, anisotropy and connectivity. Finite element analyses required highest resolution, but best predicted the biomechanical properties of the bone. MR diffusion and perfusion imaging and MR spectroscopy may provide measures of bone quality beyond trabecular micro-architecture.     

静脉性脑梗死的磁敏感加权成像表现

目的 研究静脉性脑梗死的磁敏感加权成像(SWI)表现及其临床应用价值.资料与方法 回顾性分析25例经MR或DSA确诊的脑静脉窦血栓(CVST)患者的影像资料,所有患者均伴有静脉性脑梗死.25例均行T_1WI、T_2WI、2D T_2~*梯度回波(GRE)、SWI及磁共振静脉成像(MRV)检查.其中,18例行DSA检查,22例行CT检查.结果 20例为出血性静脉脑梗死,5例为非出血性静脉脑梗死.SWI示16例(16/20)出血灶的数目较TISE序列增多,显示18例(18/20)的出灶灶较T_2FSE增多,显示12例(12/20)的出血灶较2D T_2~* GRE序列增多.其中,17例(17/25)的SWI最小强度投影(MinIP)图像梗死区可见许多扩张的小静脉,其他序列未见此征象.结论 SWI可以发现静脉性脑梗死中更多的出血灶和扩张的引流静脉,对诊断静脉性脑梗死和判断静脉性脑梗死患者的病情可能会有更大帮助.